Study on epoxy novolac and carbon-fiber reinforced epoxy novolac composites for use as implant materials. Part 2. Physico-chemical properties

We investigated the physico-chemical properties of epoxy novolac resin cure d with 4,4-diaminodiphenylsulfone (EPR) and carbon-fiber reinforced epoxy n ovolac composites (EPC), using FT-IR, SEC, and GC-MS methods. Material prop erties, such as epoxy equivalent weight, viscosity, and average molecular w eight were determined. Structural analysis data obtained with FTIR enabled the identification of chemical species of EPR and EPC and their extracted c omponents. Uncrosslinked resin and low molecular weight components, such as n-butylbenzylsulfonamide, diphenylsulfone, and bisphenol A, were extracted in very low concentration using the solvents DCM, DMSO, and acetone. DCM p roved to be the most suitable extracting agent. The extracts showed that po st-cure occurs during the vapor sterilization process at 134 degrees C. The physico-chemical properties of EPC, however, did not change significantly. The sorption curves of water in EPRand EPC, measured in Ringer's solution at 37 degrees C and at 60 degrees C, and the diffusion coefficients, determ ined by both short- and long-time approximation, indicated a not totally Fi ckian diffusion behavior and a maximal matrix sorption of about 3 wt%. With in the accuracy of the measurement, the activation energies of water diffus ion, estimated according to the Arrhenius equation, were equal for EPR and EPC.